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No. 6 

A Dollar's Worth of Condensed Information 

Punch and Die 
Work 

Third Edition 

Price 25 Cents 

CONTENTS 

Principles of Punch and Die Work, by E. R. Markham 3 
Suggestions for the Making and Use of Dies - - 31 
Examples of Dies and Punches, by F. E. Shailor - 41 



The Industrial Press, 49-55 Lafayette Street, New York 
Publishers of MACHINERY 

i^V,^___^^5 COPYRIGHT, 1911. THE INDUSTRIAL PRESS, NEW YORK 




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EACH NUMBER IS ONE UNIT IN A COMPLETE 

LIBRARY OF MACHINE DESIGN AND SHOP 

PRACTICE REVISED AND REPUB- 

LISHED FROM MACHINERY 



NUMBER 6 

PUNCH AND DIE WORK 

'' Third Edition 

CONTENTS 

Principles of Punch and Die Work, by E. R. Markham 3 
Suggestions for the Making and Use of Dies - - 31 
Examples of Dies and Punches, by F, E. Shailor - 41 



Copyright, 1911, The Industrial Press, Publishers of Machinebt, 
49 35 Lafayette Street, New York City 



^^"'^'^ 



//- /f/f 

©CI.A278923 



0^ 



CHAPTER I 



"V. 



PRINCIPLES OF PUNCH AND DIE 'WORK* 

Under the head of punch and die work is generally included all the 
various tools used in blanking pieces from commercial stock; bending 
stock to shape; drawing out articles from sheet stock; and all the 
different operations performed with punching, drawing and forming 
presses. The most common forms of tools to be considered are the 
dies used for blanking articles from sheet stock, called blanking dies. 

Blanking Dies 

A set of blanking dies consists of a male die, or punch, as it Is 
generally termed, and a female die, or die block. These terms are gen- 
erally abbreviated and the set is called a punch and die. Blanking 
dies are generally considered as belonging to one of three classes: 
First, plain (or simple) dies; second, gang dies; and third, compound 
dies. 

When punches and dies are used in a punch-press, and are to con- 
stitute a part of the regular equipment of the shop, they are held in 
suitable permanent fixtures. Dies are held in position on the bed of 
the press by means of a "holdfast," the name of which differs in 
different shops. Some of the more common names are chair, chuck, 
bolster, and die holder. Dies large enough to warrant it are clamped 
to the bed of the press, thus doing away with the necessity for hold- 
ers. Dies are fastened in place in the die holder by several methods, 
the most common of which is by means of screws, as shown in Fig. 1, 
in which a is the die and & the holder. Having screws on both sides, 
it is an easy matter to adjust the die, loosening the screws on one 
side, and forcing the die over by those on the opposite side. 

When the die is small, it is generally held in a shoe, as shown In 
Fig. 2. The manner of fastening the die in the shoe usually depends 
on the designer. In some shops the shoe is dove-tailed as shown, the 
angle being from 10 degrees to 15 degrees less than a right angle; the 
slot is made somewhat tapering. The die is given a corresponding 
taper and angle on its sides, and, to fasten it in position, it is driven 
securely in place. The amount of taper given the slot in the shoe must 
not be great, or the die will jar loose when in use. A taper of one-half 
inch per foot of length answers nicely. In other shops the shoe is made 
with a groove, as described above, only it is from \i to % inch wider 
than the dies, which are held in place by means of a taper key or 
wedge, as shown in Fig. 3. When making this form it is necessary 
to make the dies of equal width on their ends. This method does not 
require so great a degree of accuracy when machining the die block. 

• Machinery, July, August and September, 1906. 



4 No. 6— PUNCH AND DIE WORK 

A third method consists in making a shoe having the back of the 
slot planed at the angle mentioned, while the front wall is made 
square with the bottom, the die being held with setscrews, as shown in 
Fig. 4. If this form is used, care must be exercised when laying out 
the screw holes, so that they do not come in line with the screws in the 
bolster when the shoe is in its proper place; and, again, the screws 
must not press on any portion of the die immediately in line with the 
opening, or it will be closed somewhat when pressure is applied to the 
screws. Fig. 4 shows the screws pressing on the solid portion of the die. 






Fig. 3 





[1 


'Ml) 



Macl.nicr;). .V. F. ° 

Figs. 1 to 4. Various Methods of Holding Work 

Dies which are fastened in bolsters without using a shoe must have 
their sides machined at an angle, as in Fig. 1, to prevent them lifting 
from the strain incident to removing the punch when it has pierced 
the stock. The angle should be from 10 degrees to 15 degrees, some 
mechanics- claiming best results with 20 degrees. The latter, however, 
seems greater than there is any necessity for on ordinary work. 
Kind of Steel Used for Die Work 

For most work the stock used in making punches and dies should 
be a good quality of tool steel. A die that has cost from 5 dollars to 
100 dollars for labor is as liable to crack when hardening as though 



ELEMENTARY PRINCIPLES 5 

the same steel had been made into any other form of tool; and in 
fact its shape and irregular thickness of stock at various points, 
together with numerous sharp corners that are liable to be present, 
make a tool that requires extreme care in handling when hardening. 
A good grade of tool steel, free from harmful impurities, is less liable 
to crack then an inferior grade, and the slight difference in cost is 
offset many times by the cost of labor in the die construction. This 
does not necessarily mean that a higli-priced steel must be used for 
this class of work; simply a good quality of steel, low in percentage of 
those impurities which cause trouble when the steel is hardened. 
When we speak of good, reliable steels, we do not necessarily mean 
high-priced steel. 

If best results are desired when hardening, the steel should be 
annealed after the outer surface of the piece has been removed and 
the opening blocked out somewhere near to shape. 

In all shop operations true economy should always be practiced, and 
many times this may be done by a saving of tool steel. If a die is 





F,>:. 6 



Q8B8B^ 



. 5. Cast Iron Body Die, used 
with Tool Steel Bushings 



. 7 

chinttry, iV. r. 



Figs. 6 and 7. Method of Removing 
the Stock in a Solid Die 



like Fig. 5, a saving may be effected by making the body of cast iron 
and inserting bushings of tool steel; and if we wish at any time to 
make a new die, we simply make the bushings, and if ordinary care 
is taken, the holes will be concentric and consequently the proper dis- 
tance apart, so there will be no necessity of altering the location of 
the punches, as might be the case if a die made of a solid piece was 
hardened. 

General Principles of Die Making 

When a number of dies are to be made to fit the same holder, they 
may be planed to size in the bar and then cut apart by means of the 
cold-sawing machine. It will be necessary to plane again the side of 
dies that must fit a shoe of the style shown in Pig. 2, as one end must 
be wider than the other. This may be effected very readily by having 
a strip of cast iron planed to the proper taper to place the die on when 
planing or milling. The face of the die must be smooth in order 
that the outline traced on it may closely correspond to the templet. 
If the surface is a succession of ridges, the scriber will not closely 



6 No. 6— PUNCH AND DIE WORK 

follow the edges of the pattern, and the figure traced will be larger 
than desired. After the face has been made smooth by planing, grind- 
ing or filing, the surface may be coated with blue vitriol solution, 
or it may be heated until it assumes a distinct straw or blue color, 
and the outline of the piece to be punched laid out. 

If the die is what is known as a solid die, that is, made from one 
piece of stock, it may be laid off and prick-punched as in Fig. 6, after 
which holes may be drilled, leaving the face of the die as in Fig. 7, 




Machi-iify, S.T. 
Fig. 8. Die Milling Machine 

after which the core may be removed. When drilling for the opening, 
first drill any portions which are to be left circular or semi-circular 
in shape. These are then reamed from the opposite side with a taper 
reamer that will give the desired amount of clearance. When drilling 
to remove the core mentioned, some tool-makers use drills of sizes 
that break into the next hole. After drilling all way round, the core 
drops out of its own accord. If this method is adopted, best results 
follow the use of the straight-fluted drill. Fig. 9. Others drill with 
drills of the size of the pilot of a counterbore, and after drilling all 
the holes, the counterbore is run through. Of course, it is understood 



ELEMENTARY PRINCIPLES 7 

that in laying off for the holes, they are located so that the counter- 
bore breaks into the next hole. A third method consists of laying off 
and drilling holes so that there is a little stock between the holes after 
drilling, which is broken out by means of a drift driven in from each 
side until the cuts meet. In this way the stock is cut away and the 
core removed. 

After taking out the core, the die may be placed in a die milling 
machine, or a die sinking machine, and by the use of a tapered mill- 
ing cutter the stock may be removed and the desired angle of clear- 
ance given the walls of the hole. The angle of clearance necessary for 
best results cannot be arbitrarily stated, but varies according to the 
character of the work to be done with the die. In the absence of 
either of the milling machines mentioned, a universal or a hand miller 
may be used. There are various slotting devices which may be attached 
to universal milling machines which are used advantageously on work 




Machinery, N. V, 



Fig. 11 

Fig-s 9, lO and 11. Tools used in Die-making' Machines 

of this character. During the past few years several vertical filing 
machines have been placed on the market which are recommended 
highly for the purpose of working the openings of dies to shape. If 
a die milling machine. Fig. 8, is used, the form of taper milling cutter 
shown in Fig. 10 is employed. As the milling cutter is driven by a 
spindle beneath the die, the cutting portion extending up through 
the opening, with the face of the die uppermost, the small part of the 
cutting portion should be at the end of the cutter. If a die-sinking 
machine, Fig. 12, is used, a cutter like Fig. 11 is employed. After 
working the opening to shape and size as nearly as possible with the 
milling cutter, it may be finished by filing. 

Clearance 
When finishing the opening to shape and size it is necessary to get 
the desired clearance and to have the walls of the opening straight, as 
at o a in Fig. 13, rather than rounding as represented at a a in Fig. 14. 
The amount of clearance differs for various work and ranges from 
one-quarter to three degrees. The greater amount is seldom given un- 
less it is necessary that the blank fall from the die each time one 
is punched. Another instance where it is desirable to give excessive 
clearance is where a punch with a crowning face, as in Fig. 15^ is 
used for punching stiff stock. 



8 



No. 6— PUNCH AND DIE WORK 



When a milling machine with a slotting attachment, Fig. 17, is used, 
sharp corners may he cut to the line, as may certain irregular sur- 




Fig. 12. Die-sinking 
Machine 



Fig. 17. Die-slotting Attachment 
for Milling Machine 





r^<^ 



Fig. 13 





Fig. 14 



Fig. 15 



ilacMneri/ .Y. T, p- .| g 



Figs 13 and 14 Correct and Incorrect Relief. Fig. 15. Punch Crowned for Stiff Slock. 
Fig. 16. Templot for Gaging Relief 

faces which could not be shaped with milling cutters. Of course, it 
would be necessary to have cutting tools of the proper shape to ma- 



ELEMENTARY PRINCIPLES 9 

chine the forms mentioned, the advisability of making which would 
depend on whether it would be cheaper to make the necessary tools 
and to do the machining, or file to the desired shape. A fixture known 
as a die shaper, whose action resembles the slotting device described 
above, is made to attach to a milling machine and works the same 
as the other attachment. 

In order to gage the angle of clearance it is advisable to have angle 
gages. Several of these may be made and kept in the tool chest and 
should be of the more common angles used. They may be of the 
form shown in Fig. 16, with the angle stamped on the heavier portion. 

Shear of Punches and. Dies 

The cutting faces of dies are given shear for the same reason that 
the teeth of milling machine cutters are cut helical or spiral. The 
shear makes it possible to cut the blank from the sheet with less 
expenditure of power; it also reduces the strain on the die and punch. 
While it is customary to shear the face of the die when possible, 
there are instances when it is advisable to leave the face of the die 




Fig. 18. A Piece of Work for 

■which the Punch Should be 

Provided with Shear 




Mixchinert/j A'. '. 



Fig. 10. A Case where the Shear should be 
on the Die 



flat and shear the punch. The shear is given to the punch when the 
stock around the hole is the desired product and the stock removed is 
scrap, as in Fig. 18. The face of the die is sheared when the portion 
pressed through the die is the product, as at a a in Fig. 19, which also 
illustrates the shear of the die. 

The amount of shear necessary to give a die to obtain best results 
depends a great deal on the thickness of the stock to be punched, and 
also on the length of the piece to be removed, and on the power of 
the press. The shear of a die usually commences at the center and 
extends toward each end, as in Fig. 19, the punch being left flat on 
its face. When the punch descends, the cut commences at the highest 
point of the die, which is in the center, and continues toward each 
end. The portion at the center will have been removed from the stock 
before the cut has progressed very far toward the ends, and in this 
manner the cut is distributed over the length of the piece, reducing 
the strain on the press and tools. 

The diemaker, if he works to drawings furnished him by the drafts- 
man, makes the thickness of die and length of punch to correspond 
with dimensions. However, it is customary in shops where few dies 



10 



No. 6— PUNCH AND DIE WORK 



are made and no draftsman is employed, to give the diemaker or 
toolmaker an idea of the shape and dimensions wanted, or possibly a 
templet, and he is required to go ahead and "work out his own salva- 
tion." In such cases the workman must first find the dimensions of 
the press to be used, the distance from the bed to the ram, the length 
of stroke of the ram, the amount the ram may be adjusted, the thick- 
ness of the bolster, and particulars about any shoes that are to be 
used. These things should be carefully set down and kept where the 
workman may have access to them at any time. If there are several 
presses, each should be marked and the dimensions of each carefully 
recorded, according to the work of the individual machine. If this 
precaution is followed and the dimensions taken into consideration 
when machining the die and punch, there need be none of the trouble 
sometimes experienced, such as a die too thick or a punch too long, 
or the reverse, for the press in which they are to be used. 

Stripping the Stock 

When articles are punched from sheet stock, or in fact from any 
stock where the scrap is around the punch, the stock will be carried 





Fig. 20. Example of Stripping Plate 



upward when the punch ascends, unless some device is furnished to 
prevent its doing so. Fig. 20 shows an arrangement o called a strip- 
per, or stripping plate, the opening in this being a trifle larger than 
the punch. The stripper plate must be securely fastened to the die, 
or the die holder, and must be stiff enough to prevent its springing 
when in use. Between the stripper and the die (at 6) is a guide 
against which the stock being operate! on rests, and which determines 
the amount of scrap at the back edge of the sheet. This guide is 
made of a thickness that insures the space between the die and 
stripper being somewhat greater than the thickness of the stock used; 
in fact, the space must be sufficient to allow the stock to move along 



ELEMENTARY PRINCIPLES 



11 



easily even when the surface is made somewhat irregular by the 
operation of punching. At c is a guide pin or stop against which the 
stock is placed to determine the endwise setting. 

Templets 

When dies are made for producing pieces that must be of a given 
size and shape it is necessary to have a piece of the same shape and 
size to work to; this is called a templet. At times it requires a con- 
siderable degree of skill to make a templet that will answer for the 
work in hand. As an example, the templet shown in Fig. 21 may be 
referred to. After blanking and turning the ear at the top of the piece 
to be made, it was to be closed on a groove in an axle, as shown in 
Fig. 22. After closing, the outside of the washer was supposed to run 
about true. The die was made to a templet and it was found less 
difficult to make the die than the templet. In this instance it was 
necessary to make two pieces of the desired shape exactly alike, one of 
which was closed on the model axle and tested. The points that were 
not right were located on the one that had not been closed up. Then 
others were laid out from it, due allowance being made for the im- 




Fig. 2» 





fk- 22 



KacUnery,S.Z^ 



^ ) 



Fig. 23 F'^- 24 

Figs. 21 to 24. Example of Templet Making 

perfections of the first. When making, two pieces of stock v/ere placed 
together, and one half was worked to the laying out lines as in 
Fig. 23. After the other half had been blocked out somewhere near 
the line, the pieces were reversed and each half that had been blocked 
out was finished to the finished half, as indicated. In this way the 
ends were exactly alike and the two being machined, or filed together, 
were, of course, alike. When one was forced down or closed on the 
axle and was found correct, the other answered for the templet to 
be used in laying out the die, and afterward to fit the opening, too. 
While the example related was comparatively simple, it did not appear 
altogether simple to one not accustomed to that class of work, and it 
serves to illustrate the idea brought out. 

In order that templets may be easily handled, it is customary to 
attach some form of handle to them, which is sometimes done by drill- 
ing and tapping a hole in the templet, and cutting a short thread on a 
piece of wire which is screwed into the tapped hole. Another common 
method is to attach a piece of wire by means of a drop of solder, as 



12 



No. &-PUNCH AND DiE WORK 



shown in Fig. 24. This method is open to the objection that the wire 
must be removed from the templet when it is used in laying out the 
punch, as it is necessary, when the templet differs in shape on two 
edges, to lay opposite sides of the templet against punch and die. 

Sectional Dies 

Dies are many times made in two or more sections in order to facili- 
tate the operation of working the opening to shape. In other cases 
the die, if solid, would be so large as to render it well-nigh impossible 
to harden it in a shop with only the usual facilities for doing work 
of this class. And then again if it should go out of shape in harden- 
ing, it would be a difficult task to remedy the defect. If made in sec- 
tions, as shown in Fig. 25, it would be possible to peen or grind to 
the original shape with little trouble. 

A die of the design shown in Fig. 26 may be made sectional be- 
cause It is much easier and cheaper to make than if solid. The sec- 



W 



I I 



Fig. 25. Sectional Dio held by Screws 







Machinery, iV'. i*. 
Fig. 26 Sectional Die Located by Taper Pins 

tions are held in their proper location by dowel pins. They are held 
together by the shoe which secures them in the press. If the die is 
comparatively small, the circular shapes at each end and center are 
produced by first drilling, and then reaming from the back, with a 
reamer of the proper angle. The sections may be separated and the 
balance of the stock removed in a shaper, planer or milling machine. 
When this stock is removed the die may be held at the proper angle 
to produce the desired clearance. After machining as close as possi- 
ble, the surfaces may be finished with a file and scraper. 

When the opening has been finished to the templet, the top may be 
giren the proper shear. In order to facilitate the operation of grind- 
ing -when the die is dull, the stock may be removed, as in Fig. 27, leav- 
ing about 1/4 inch on each side of the opening at the narrowest portion. 



ELEMENTARY PRINCIPLES 



13 



There are certain forms of dies where it is not feasible to cut away a 
portion of the top, as shown, but where it can be done it saves much 
time when grinding. 

Correcting- Mistakes Made in Dies 

Should the workman, through misunderstanding or carelessness, 
make the opening too large at any point, he should not attempt to 




Machinery^ iV. K. 
Fig. 27. Method of Cutting away the Top of Die to Facilitate Grinding 

peen the stock cold, as is sometimes done, for while it is possible 
to do this and then finish the surfaces in such a manner that it will 
be scarcely noticeable, the stock directly below where the peening took 
place will almost surely crack during the life of the die. 

Should the mistake referred to occur, heat the die to a forging heat, 
when the stock may be set in without injury to the steel. When set- 




Machineryj N. V, 
Fig. 28. Closing up a Die which is too Large 

ting in, a blacksmith's fulling tool may be used, this placed on the 
face of the die and struck with a sledge, as in Fig. 28. If there is 
objection to disfiguring the top surface of the die, this method can, of 
course, not be used, but if the top is to be cut away, as shown in 
Pig. 27, the depression made by the fulling tool would be entirely cut 
away. It is never good practice to bend, set in, or otherwise alter the 
form of steel when cold, if it is to be hardened, as such attempts 
nearly always end in a manner entirely unsatisfactory. 



14 



No. 6— PUNCH AND DIE WORK 



Re'working' Worn Dies 

When a die becomes worn so that the opening is too large, or the top 
edge of the -walls of the opening are worn so that the die is "bell muz- 
zled," it may be heated to a forging heat, set in with a fulling tool, or 
a punch of the desired shape, after which it is reheated to a low red 
and annealed. After annealing it is reworked to size. This rework- 
ing, care and judgment being- used, gives excellent results, and effects 
a considerable saving, as otherwise it would be necessary to make new 
dies, while the die may be reworked at a fraction of the expense of a 
new one. 

When making a sectional die, it is possible in case the opening is a 
trifle too large, to work a little stock off the faces that come together, 
provided the outer edges have not been planed to fit the holder; also, 




JiJriclMiri/iKy, 
Fig. 29. Arrangement of Oil Cooling Bath 

if it is allowable, these surfaces may be cut away the desired amount, 
and a strip of stock of the proper thickness placed between the die 
and holder. Considering the liability of a mistake taking place when 
the beginner is doing work of this kind, it is, generally speaking, 
advisable to leave the fitting of the die to the holder until the opening 
has been worked to size. 

Hardening' Dies 

There is probably no one article the hardener is called on to harden 
that he dreads any more than a die. If he succeeds in bringing it 
out of the bath without a crack, he gives the credit to "luck"; and 
if it cracks, it is almost what he was looking for. This is an unfor- 
tunate condition, as there is no need of losing dies in the operation of 
hardening. Of course, if a piece of imperfect steel is used, it is almost 
sure to go to pieces in the bath; but if the steel is of the proper 
quality and in good condition, there need be no trouble when hard- 
ening. 

When handling work so diversified in character as the class under 
consideration, the operator should not assume that it is possible to 



ELEMENTARY PRINCIPLES 



15 



adopt any set method which is not to be deviated from, as there is no 
one class of work that calls for a greater exercise of skill and common 
sense than the proper hardening of punch-press dies, unless it be the 
hardening of drop-forging dies. For most dies of this character, how- 
ever, and especially for those complicated in form, and which must 
retain as nearly as possible exact measurements, there is no method 
that will give the satisfaction derived from the method known as 
"pack-hardening." 

Pack-hardening' 

When pack-hardening such pieces, best results are derived from the 
use of a bath of raw linseed oil of the type shown in Pig. 29, in 
which the oil is kept from heating by being pumped through a coil of 




W////////////yy/////m^^^^^ 

Fig. 30. Dipping the Work in the Bath 

pipe in a tank of water, and then forced into the bath and through the 
opening as shown. If such a bath is not at hand, good results can be 
obtained where the oil is not agitated but the die is swung back and 
forth and moved up and down somewhat in the oil. If many dies are 
to be hardened this way, however, it is necessary to have a bath of 
generous proportions, or, else several smaller baths, as it would not 
do to use the oil after it becomes hot, although oil that is heated some- 
what will conduct the heat from steel more rapidly than would be 
supposed, and is better adapted for hardening than if it is extremely 
cold. 

General Directions for Hardening- 

The secret of success in hardening dies by the ordinary method 
consists in getting as nearly as possible a uniform heat. To accom- 
plish this the die cannot be heated very rapidly, as the edges and 
lighter portions would heat more rapidly than the balance of the 
piece. Unequal contraction, when quenching in the bath, follows un- 



16 No. 6— PUNCH AND DIE WORK 

even heating, and unequal contraction causes the die to crack. High 
heats cause cracks in steel. Then, again, high heats render the steel 
weak, and as a consequence it cannot stand the strain incident to 
contraction of one portion of the steel when another portion is hard, 
and consequently rigid and unyielding. Steel is the strongest when 
hardened at the proper temperature, known as the refining heat. 

Cold baths are a source of endless troubles when hardening dies. 
They will not make the steel any harder than one that is heated to a 
temperature of 60 or 70 degrees, or even warmer than this, but they 
will cause the die to spring or crack where the warmer bath would 
give excellent results. A bath of brine is to be preferred to one of 
water for this class of work, the brine being heated to the temperature 
mentioned above. 

Have the bath of generous proportions. When the die is properly 
heated, lower it into the bath as shown in Fig. 30, moving it slowly 
back and forth to the positions shown, which causes the liquid to cir- 
culate through the openings, thus insuring the walls of the opening 
hardening in a satisfactory manner. Then again, moving back and 
forth brings both surfaces of the piece in contact with the liquid, 
causing them to harden uniformly, and ]>pe,vent-jing an undue amount 
of "humping," as would be the case if one side hardened more rapidly 
than the other. The workman must, of course, exercise common sense 
when doing this class of work. If he were to swing a die containing 
sharp corners, intricate shapes, and fine projections as rapidly in the 
bath as it would be safe to do were the opening round or of an oval 
shape, it might prove disastrous to the die, as such a shape would give 
off its heat very rapidly, and as a result the fine projections and sharp 
corners would harden much quicker than the balance of the die; and 
as they continued to contract, the projections would fly off, or the 
steel would crack in the corners. To avoid this, have the bath quite 
warm, move the die slowly, and as soon as the portions desired hard 
are in the proper condition, remove the die and plunge it in a bath of 
warm oil, where it may remain until cooled to the temperature of 
the oil. 

Most of the trouble experienced when hardening dies is occasioned 
by one of two causes — possibly both. The first cause is uneven heat- 
ing, the second, cold baths. 

The Punch 

The method of holding the punch depends on its shape and the style 
of die, as well as on the holders at hand in the shop. If it can be 
made as in Fig. 34, with a shank to fit a holder which enters an 
opening provided in the lower end of the ram, it will be comparatively 
simple to make. At other times it will be necessary to attach several 
punches to a holder, as in Fig. 31. When these punches can be 
attached to the holder by means of round shanks it will be found a 
satisfactory method. For many forms of punches, however, this would 
not answer, it being found necessary to attach them by screws, dowel 
pins being provided to keep them in position, as in Fig. 32 at o. 
Then, again, it is sometimes thought advisable to use a fixture for 



ELEMENTARY PRINCIPLES 



17 



holding the punches, having a dove-tailed slot cut in the face as in 
Pig. 33, the punches having a tongue which is fitted in the slot. The 
punches are securely held by means of setscrews. As the opening In 
the lower end of the ram to receive the punch holder of small presses 
is ordinarily square, the holder is made of a shape that fits the open- 
ing, the hole to receive the punch being round. At times the holder is 




FIG. 31 



FIG. 32 



^ 



m 



SO 



o 



FIG. S3 ^Incla'ufi/.It.l: 

Figs. 31, 32 and 33. Various Methods of Holding- Punches 

split as in Pig. 35. When pressure is applied, the holder is closed onto 
the shank of the punch, thus holding it securely. At other times the 
holder is made without splitting, and a setscrew placed in the lower 
end of the holder, Pig. 36. This setscrew, when screwed against the 
punch, holds it securely in place. 

It is customary to make the die, and harden it, and then make the 



18 



No. 6— PUNCH AND DIE WORK 



punch and fit it to the die. After squaring the end of the punch that 
is to enter the die, the surface is colored with blue vitriol solution, 
or by heating it until a distinct brown or blue color is visible, after 
which the desired shape is marked on the face by scribing. If it is 
considered advisable to lay out the shape by means of the templet, it 
may be done; but if the templet is not of the same shape on its two 
edges, or the ends are different from one another, it will be necessary 
to place the opposite side against the punch, from that placed against 
the die when marking. However, it is the custom many times to 
mark the punch from the die. If the die is given shear, it is neces- 
sary to mark the punch before the face of the die is sheared. When 




FIG. 34 




FIG. 35 




FIG. 36 



Pigs. 34, 35 and 36. Punch and Punch-holders 

laying out several punches from a die which has a number of impres- 
sions, it is necessary to lay out the punch from the die. 

The surplus stock on the punch is removed by filing, chipping, mill- 
ing or planing, as the case may be, until it is but a trifle larger than 
the opening in the die. The end is then chamfered somewhat so that 
it enters the opening, and the punch is forced into the die a little way. 
It is then removed, the stock cut away, and the punch forced in again, 
this time somewhat further. This method is continued until the punch 
enters the die the required distance. It is then filed or scraped until 
the desired fit is obtained. When punch and die are to be used for 
punching paper, soft metals, or thin stock, the punch must fit nicely. 
If the stock is thick, or stiff, the punch may be somewhat looser. 



ELEMENTARY PRINCIPLES 19 

For stock ^ inch thick it is the practice many times to have a 
1/32-inch space between tlie punch and die at all points. The exact 
amount cannot be stated arbitrarily, it being governed by existing 
conditions. 

There are instances in which it is advisable to make punches some- 
what differently from the method described. When the nature of the 
stock to be punched is such as to cause it to cling to the punch, 
making the operation of stripping difficult, to the extent that any 
stripper plate put on the die would be bent, or the end of the punch 
pulled off during the operation, the punch may be made straight for a 
distance that allows of grinding several times; then the portion imme- 
diately above this may be given a taper. This tapefed portion of the 
punch is intended to enter the stock, tut not the die. Its action is to 
increase the size of the opening somewhat, thus making the operation 
of stripping possible without endangering either the stripper or the 
punch. 

Advisability of Hardening Punches 

There are various opinions among practical men as to the advisabil- 
ity of hardening punches. For most jobs it is the custom to do so, 
though there are some mechanics who consider it advisable to harden 
them, and others who do not. There are instances where punches work 
well either way, and in such cases it is, of course, a matter of opinion. 
If good results follow the use of a soft punch it may be used, and as 
the punch wears, it is upset and sheared into the die. 

There are times when a soft die and hardened punch work well, and 
times when a hardened die and soft punch give good results. At other 
times both punch and die may be left soft. Very large punches and 
dies for hot trimming of drop forgings are sometimes used, where both 
are in a soft condition, and they stand up properly. The shape of 
these, together with the size, often make it impracticable to harden 
them. It would not be advisable to state that such and such dies or 
punches should be hard or soft; it must be determined by the circum- 
stances under which they are to be used, and the decision is a matter 
of experience on that particular work. 

Directions for Hardening- Punches 

If punches are to be hardened — and it is generally considered best — 
they should be very carefully heated. It must be borne in mind that 
punches are subjected to great sti-ain, consequently they should be 
heated uniformly, and to as low a temperature as will give desired 
results, thus making them as strong as possible. Heat slowly to avoid 
overheating the corners, as these are subjected to the greatest strain. 
The distance we should harden a punch depends on the shape and 
size, and the use to which it is to be put. If it is a piercing punch 
of the form shown in Fig. 37, it should be hardened the entire length 
of the portion marked a to avoid any tendency to bend or upset when 
in use. If it is of a form that insures sufficient strength to resist 
any tendency to upset when in use, as is the punch illustrated in 
Fig. 38, then it need not be hardened its entire length. 



20 



^o. 6— PUNCH AND DIE WORK 



Pack-hardening makes an admirable method for hardening punches 
for most work, but for piercing punches of the type in Fig. 37 it is 
not advocated, as the whole structure of the steel should be as nearly 
as possible alike. Such punches should be heated in a muffle furnace, 
or in a tube in the open fire, turning occasionally to insure uniform 
results, for not only can we heat a piece more uniformly if it is turned 
several times while heating, but a fact not generally known is that a 
cylindrical piece of steel heated in an ordinary fire without turning 



FIG. 37 





FIG. 33 



FIG. 39 

Pigs. 37 and 38. Shapes Requiring Different Treatment in Hardening. 
Fig. 39. Clamp Used when Scribing Die Outline on Punch 

while heating will many times show softness on the side that was 
uppermost in the fire, no matter what care was taken when heating 
and dipping. If it is reheated with the opposite side uppermost, that 
will be found soft if tested after hardening, while the side that was 
soft before will be hard. The smaller the punch the more attention 
should be given to the condition of the bath. Luke warm brine is the 
best. Work the punch up and down and around well in the bath. 

Tempering- Punches 

It is the custom of many mechanics to draw the temper of punches 
of the description shown in Fig. 37, to a full straw on the cutting end, 
but to have the temper lower further up the punch. Better results 
follow, however, if the punch is left of a uniform hardness its entire 
length of slender portion, as it is then of a uniform stiffness, and the 
liability of springing, especially when punching stiff or heavy stock, 
is reduced to a minimum. 

It is generally considered good practice to temper the punch so that 
it is somewhat softer than the die; then, if from any accident the two 



ELEMENTARY PRINCIPLES 21 

come in contact, the die will in all probability cut the punch without 
much injury to itself. There are exceptions to this, however. In many 
shops were large numbers of dies which are hardened are used, it is 
customary to have the one which is the more difficult to make the 
harder; so it will cut the other if they come in contact with each other. 
In order to hold the die and punch blank firmly together when 





Machinery, }i\ T, 
Fig. 40. Multiple Die, and Stock Cut in Same 

marking the shape on the face of the punch, a very convenient fixture 
known as a die clamp, shown in Fig. 39, is used. When the two are 
secured by means of this clamp, it is possible to move them around 
so as to get at the various portions where we wish to scribe. 

Multiple Dies 

A reduction in the cost of manufacture is often made possible by the 
use of multiple dies, whereby two or more pieces are punched out at 
a time. In punching perforated steel work it is no uncommon thing 



22 



No. 6— PUNCH AND DIE WORK 



to see punches and dies in use where several hundred punches are 
working into one die. 

If an article, for example, of the form shown in the die in Fig. 40, 
were to be punched in lots of several thousand, the die should punch 
a number at a stroke. Such a die and the stock left are shown in 
Fig. 40, where the die is shown at A and the stock after the first 
punching at B. It will be noticed that the distance between the open- 
ings is considerable. This is necessary, as it would not be possible 
to place the openings in the die as close as they should be to econo- 




PLAN OF PUNCH 




PLAN OF DIE JiiaMnery^-.T. 

Figs. 41 and 42. Gang Punch and Die 

mize stock, since there would not be stock enough between to insure 
the die sufficient strength to stand up when working. For this reason 
the openings are located as shown. After punching as shown at B, 
the stock is moved along the right distance for the intervening stock 
to be punched out, as at C. 

Gang Dies 
If it were desirable to punch a piece like that at a in Fig. 43, it 
would be possible to make a blanking die and punch which would pro- 
duce the blank of the right size and shape, but without the holes; 
then, by means of another die, with three punches working into it, we 
could punch the holes. It is apparent that such a method would be 
more expensive than one that made it possible to punch the holes and 
the piece at one passage of the stock across the die. This may be done 
by the use of a die of the description shown in Figs. 41, 42 and 43. 
"When using this die the stock is placed against the guide and just 
far enough to the left so that the large punch h will trim the end. 
Thea, when placed against the stop or gage pin c, bring the guide pins 
in end of punch h in line with the holes punched at the first stroke of 
the press at the time the end was trimmed. 



ELEMENTARY PRINCIPLES 



23 



When the stock is purchased of the proper width for one piece, It 
is fed through and the scrap thrown aside. At times it is purchased 
just wide enough for two pieces, in which case one edge is placed 
against the guide d and the stocli fed through; after which it is 
turned over and fed through with the opposite edge against the guide, 
thus using all the stock except such portion as necessarily becomes 
scrap. 

However, if the stock is purchased in the commercial sheet, it is 
necessary to trim the edges every time a row is punched along each. 
If no power shears are located handy to the press this may prove to 
be a more costly operation than the punching, and no matter how 
conveniently such a shear may be located, the operation adds a con- 




Fig. 43. Elevation of Gang Punch and Die shown in Plan in Figs. 41 and 42 

siderable cost to the product. To avoid this trouble and expense 
another punch and opening in the die may be added. The object of 
this punch is to remove the scrap between the openings in this sheet 
and also trim the edge of the sheet, thus making it straight and in 
condition to bear against the guide on the die. The die and punch 
with the addition mentioned are shown in Fig. 44. When using a 
trimming punch as described above, it is necessary to use a stop of 
the description shown at b. The end of the scrap striking this gov- 
erns the location of the stock, and when thu punch descends the scrap 
is cut away. 

When making dies of this class it is necessary to have the blanking 
die a the longer in order that the locating pins on the end may engage 
in the holes in the stock and locate it right before the other punches 
reach the stock. It is also necessary to place the gage pin, so that 
the stock will go a trifle further than its proper location — say 0.010 
inch. Then, when the locating pins engage with the holes, they draw 



24 



No. 6— PUNCH AND DIE WORK 



the stock back to its proper location; whereas if the tool-maker 
attempted to locate the stop exactly, any dirt or other foreign sub- 
stance getting between the end of the scrap and the stop would cause 
trouble. 

Bending Dies 

While it is possible, in certain cases, to bend articles during the 
operation of punching, it is usually necessary to make a separate oper- 
ation of bending. There are instances where bending fixtures which 
may be held in a bench vise, or attached to the bench, answer the 



I — I 



-^ 



XT- 



XT 



WW 




Fig. 44. Gang Punch Arranged to U.se Sheet Stock 

purpose as well and allow the work to be done more cheaply than if 
bending dies were used. But as a rule the die used in a press provides 
the more satisfactory method, and allows the work to be done at a 
fraction of the cost. 

It is sometimes possible to make the dies so that the various oper- 
ations can be done in different portions of the same die block, the piece 
of work being changed from one portion to another lu order as the 
various operations are gone through. At other times it is necessary to 
make several sets of bending dies, the number depending on the num- 
ber of operations necessary. When a "batch" of work has been run 



ELEMENTARY PRINCIPLES 



25 



through the first die, it is removed from the press and the next in 
order placed in, so continuing until the work has been brought to the 
desired shape. 

"When a comparatively small number of pieces are to be bent to a 
shape that would require a complicated and consequently costly die in 
order that the work might be done at one operation, it is sometimes 
I'onsidered advisable to make two dies, which are simple in form and 
inexpensive to make, to do the work. At times the design of the press 
is such that a complicated die could not be used; and as a result addi- 
tional dies of a simpler form, and which can be fitted in the press, must 
be made. 

We will first consider the simpler forms of bending dies. Fig, 45 
represents a die used in bending a piece of steel, A, to a V-shape, as at 
B. In the case of a die of this form it is necessary to provide an 





FIG. 45 




FIG. 4G 



FIG. 47 JIlachi-ntTyJf.y. 
Figs. 45, 46 and 47. Examples of Bending Dies 

impression of the proper shape as shown; this impression, if the die 
is to be used for bending stiff stock, must be of a more acute angle 
than if stock having little tendency to spring back when bent to shape 
be used. Under ordinary circumstances the upper portion or punch 
would be made of the same angle as the die. It is necessary to provide 
guides and stops as shown to locate the work properly. 

If the stock used in making the pieces is of a high grade and the 
product is a spring or similar article which must be hardened, it will 
be found necessary to cut away the die somewhat in the bottom of the 
impression, making it a little different in shape from the punch, as 
shown in Fig. 46. This is to prevent crushing or disarranging the 
grain of the steel to an extent that would cause it to break when in use. 



26 



No. 6— PUNCH AND DIE WORK 



If the die is of the form shown in Fig. 47, it is, of course, necessary 
to make the length a of the punch shorter than the distance across 
the opening of the die. It must be somewhat shorter on each end 
than the thickness of the stock being worlved. If possible, the upper 
corners b 6 of the die should be rounded somewhat, as the stock bends 
80 much easier and with less danger of mutilating the surface than 
T/hen the corners are sharp. When bending thin ductile metal the 
corners need but little rounding. If the stock is thick, or very stiff, a 
greater amount of rounding is needed. 

While the form of bending die in Fig. 45 answers for ordinai-y work, 
there are jobs where such a die would not insure a degree of accuracy 
that would answer the purpose, and it will be found necessary to make 
one similar to Fig. 48, where a riser or pad a is provided, as shown. 




yfachinery, K. T. 
Fig. 48. Bending Die for Accurate Work 

This is forced upv.ard by the spring b and is gaged as to height by 
means of the washer c bearing against a shoulder, as shown. It will 
be observed that the spring gets its bearing against the washer, which 
in turn bears against the shoulder of the riser as mentioned before. 
When making this die, the hole is drilled and reamed and the groove 
milled or planed for the riser, which is put in place sufficiently tight to 
hold it while the V-groove is cut, after which it may be relieved until 
it works freely. The spring b gets its lower bearing on the die 
holder. If it Is considered advisable, a screw may be provided for the 
spring to rest on. By adjusting this screw, any desired tension may be 
given the spring, although, generally speaking, this is not necessary. 

When bending articles of certain shapes it is necessary to design the 
tools so that certain portions of the piece will be bent before other 
portions. Should we attempt to make the tools solid and do the work 



ELEMENTARY PRINCIPLES 



27 



at one stroke of the press, the piece of stock would be held rigidly at 
certain points and it would be necessary to stretch the stock in order 
to make it conform to other portions of the die. In the case of articles 
made from soft stock, this might be accomplislied, but the stock would 
be thinner and narrower where it stretched. However, as a rule it is 
not advisable to do this, and dies are constructed to do away with this 
trouble. 

Fig. 49 represents a die, the upper part of v/hich has the portion a 
so constructed that it engages the stock first. After forcing it down 
into the impression in the lower portion, part a recedes into the slot 




Fig. 49. An Example of Progressive Bending Die 

provided for it. The coil spring shown is sufficiently strong to over- 
come the resistance of the stock until it strikes the bottom of the im- 
The article is shown bent at &. 



pression. 



Compound. Bending Dies 



Compound bending dies are used very extensively on certain classes 
of work, especially in making looped wire connections and articles of 
thin sheet stock. Fig. 50 shows a die used for bending a bow spring. 
As the punch descends, the stock is bent down into the impression in 
the lower half and forms the stock to a U-shape. As the end of the 
punch with the stock comes in contact with the bottom of the impres- 
sion it is forced into the upper portion, the spring keeping it against 
the stock, while movable slides — side benders — b are pressed in by 
means of the wedge-shaped pins so as to force the upper ends of the 
loop against the sides of the punch as shown in Fig. 51, forming the 
piece as at B. When the punch ascends, the finished loop may be 
drawn off. If the stock used is stiff it will be necessary to make the 
punch somewhat smaller than the finished size of the spring, as it will 
open out somewhat when the pressure is removed. 

When making looped wire work, a loop may be formed and the wire 
moved along against a stop, another loop formed, and so on, as in 
Fig. 52 When forming looped wire work it is customary to make the 



28 



A^o. 6— PUNCH AND DIE WORK 



punch ball-shaped rather than as shown in Fig. 50. The ball answers 
well on wire work and allows of the easy removal of the loop. It 
is sometimes desirable to close the upper end of an article nearly 
together, and if the stock used is extremely stiff, as bow springs made 
from a grade of tool or spring steel, it may be necessary to heat the 




Fig- 50. Die for Bending^ Bow Springs 

bow, which has previously been bent, red hot, and finish bend it by 
a special process. In the case of articles made from a mild grade of 
stock the whole bending process may be accomplished in one operation 
by substituting a mandrel, as shown in Fig. 53, for the cylindrical 
portion of the punch. 




51. Action of Die in Fig. 50 



A great variety of work may be done by modifications of the meth- 
ods for bending shown. Where but a few pieces are to be bent it is not 
advisable to go to the expense of costly bending dies; but when the 
work is done in great quantities, they will produce work uniform in 
shape at a low cost. Blanking and bending dies are made which not 
only punch the article from the commercial sheet, but bend it to the 
desired shape at the same operation. As a rule, it is advisable to 



ELEMENTARY PRINCIPLES 



29 



blank the article at one operation and bend it at another, but there 
are certain forms of work v/here it is possible to do it in a satisfactory 
manner at one operation and at a cost not exceeding that of the ordi- 




Figr. 52. 



XaeUneryJf. T, 
Successive Loops Formed in a "Wire 



nary blanking operation. This also effects a saving in the cost of 
tools, as the special bending die is dispensed with. 

Fig. 54 represents a punch and die used in punching the shoe a 
to the proper shape shown, while Fig. 55 is one used for producing 




Machi;icry,Kr. 
Fig-. 53. Forming a Bow Spring wiUi Ends which nearly meet 

the tension washer shown. Gun and other irregular shaped springs are 
many times punched to form by this style of die, although, when stock 
suitable for use in making springs is employed, it will be found neces- 
sary to make the face of the punch somewhat different in shape from 




Fig. 54. Punching and Bending at One Operation 

that desired, as the piece will straighten out more or less after it is 
punched. 

If it is desired to curl a form on a piece of work, making a loop 
as in Fig. 56, it is accomplished by various methods, sometimes by a 
modification of the die in Fig. 51. A die of the description shown in 
Fig. 57 is used wuth excellent results. In making this die, the blank 
a is first machined to size. The hole & is drilled and reamed to size, 



30 



No. 6— PUNCH AND DIE WORK 



and polished to produce very smooth walls. This may be accom- 
plished by using a round revolving lap of the right size. The slot is 
then milled as shown. If the die is not intended for permanent use 
and the stock is comparatively soft or easily bent, it need not be hard- 




Pig. 55. Making a Tension W^asher 

ened. If, however, it is to be used right along, it must be hardened. 
This is best accomplished by pack-hardening, being sure that the 
heat is low. As when using this method the die is quenched in oil, 
there is little or no danger of its going out of shape. It is then drawn 



X 



7 



BIANK BEFORE CURLING 



K 



AFTER CORLINO 



a h 




FIG. 57 Mnchir.eri/,lf.r. 

Pig's. 56 and 57. A Curling Die and its Work 

to a full straw color. The punch is made with a V-shaped impression 
in its face, as shown. This may be flat in the bottom, as indicated, or 
left sharp, as desired. 

It is possible with presses and tools adapted to the work to form 
pieces to shapes that to one not familiar with this class of work would 
seem well-nigh impossible. 



CHAPTER II 



SUGGESTIONS FOR THE MAKING AND USE OP DIES 

In the phenomenally rapid progress made during the last decade in 
the press working of sheet metals by the introduction of compound, 
combination, sub-press, and gang dies, automatic roller and dial 
feeds, the simpler operations on the power press, instead of becoming 
subject to similar improvement, have been sadly neglected. It is there- 
fore not out of place to refer, shortly, to the basic elements of the 
art of using and making dies. Although the following discussion 
originally was intended to apply to one particular line of presses, the 
suggestions brought forv/ard may be applied with slight modifications 
to any make of upright power press on the market to-day. 

It is not so generally known as it should be that the inclining of a 
press adds materially to its productive capacity. This advantage is 
almost doubled when the same belt may be used in both positions, 
permitting the change to be readily made without undue loss of time. 
Many users make it a rule to incline the press on all operations except 
"push through" jobs, that is, on all work which does not drop through 
the bed of the press. It is then simply necessary to feed the work 
to the dies, allowing it to drop out by gravity. To permit the use 
of the same belt for both positions, the press should be so placed on 
the floor that the center of the shaft when in its inclined position 
is the same distance from the line shaft as it is when the press is 
upright. 

While there are many diemakers who advocate the use of a sepa- 
rate cast iron bolster for each die, it is advantageous to use bolsters 
made of cast steel, which are largely used by Western shops. There 
are two made for each press, one for cutting dies and one for bending 
and forming dies, the construction of compound and combination dies 
remaining unchanged. By this system the separate dies are inter- 
changeable on any press; they occupy less space on the shelves of 
the tool-room, and inasmuch as all strippers and gages are fastened 
directly to the die instead of to the bolster, they never become lost 
when changing from one job to another. The desirability of using 
standard hexagon head cap screws to hold down strippers, gages, etc., 
should be impressed upon diemakers. The strippers on any die may 
then be removed to facilitate correct setting of the die, and then 
replaced in position — something impossible on slotted head sci-ews 
except by using an angle screw-driver. 

There is little room for improvement in the cast iron punch-holder. 
One might suggest, however, the use of solid piercing punches in place 
of the drill-rod surrounded by a soft steel sleeve riveted to a punch-pad. 
Wherever possible, it is advisable to do away with the old-fashioned 
soft steel punch sleeve, and to let the punches into their holders 



32 



No. 6— PUNCH AND DIE WORK 



either by turning a round shank on them, or dove-tailing them into the 
cast iron holder in the same manner as the die. 

In planing up the die-blank it is well to remember to take a very 
slight cut from the bottom and a cut about twice as deep from the top. 




Fig. 58 Fig. 59 

This removes the decarbonized surface from the cutting face where it 
needs most to be done, but leaves it on the bottom where the die may 
remain soft. Where there is a scarcity of 10-degree parallels, two 
pieces of drill-rod between the jaws of the vise may be arranged to 



% 



iii 



u 




11:; 



pcfi 




I 1 I 
.i. 



W\^ 



-m. 



1-^: 



Fig. 60 Pig. 61 Fig. 62 

Steps in the Evolution of Press Tools for Copper Connectors shown in Pig. 65 

give the correct angle, as shown in Fig. 58. Quarter-inch drill-rod is the 
size to use when the jaws are 1 9/16 inch high. Where intricate 
shapes must be drilled out with small drills, the holes may be laid 
out a trifle close together, and the shank of an old drill of the same size 



SUGGESTIONS IN DIE MAKING 



33 



pushed into the first hole drilled. This will prevent the drill from 
running too far into the previously drilled hole, and by proceeding 
in this manner all around the outline, the core to be removed will 
drop out without the use of chisel or drift. The amount of draft on 
some blanking dies which are combinations of drilled holes, as, for 
instance, the shape in Fig. 59, may be infallibly obtained by reaming 
these holes from the back of the die as though they were simple 
piercing dies. Where extreme accuracy is essential, or a die is too 
large to be made of a single forging, the use of sectional dies becomes 
imperative. While the first cost of a well-made die of this kind is 
higher than that of a solid die, still the ease of repair and uniformity 
of production of this type of die make it advantageous in the long run. 
The dies shown in the illustrations serve to emphasize the main 
features of this discussion. Fig. 60 shows a die as originally made 
for the three copper connectors shown in Fig. 65. It is a plain cut- 
ting-off die, having the different holes placed in the die at the proper 
center distances apart. By means of a suitable adjustable gage and 
by placing one of the piercing punches in its proper position in the 
punch-holder, the three different sizes of connectors shown in Fig. 65 





Fig. 63 



Fig. 64 



Fig. 65 



may be produced. However, during the process of improvement of the 
device on which these connectors were used, it became necessary to 
change the center distances between the holes and also to produce 
three longer ones. The die shown in Fig. 61 was at first considered 
adequate, but, on account of the quantity required, the scrap produced 
by the cutting punch was considered objectionable. Leaving the pierc- 
ing punches in the same position, the shape of the cutting-off punch 
was changed, as shown in Fig. 62, and a corresponding V-groove 
planed in the die. In connection v/ith stripper and gage (not shown) 
this die allows the production of an indefinite number of connectors of 
different center distances. 

The die shown in Fig. 66 impresses the fact that the slitting shear is 
a valuable auxiliary to any press. The metal for the production of 
the copper segment % inch thick, shown in Fig. 64, ordinarily would be 
cut a little wider than the length of the blank so as to allow the punch 
to cut all around. But in all cases where at least two sides of a blank 
are parallel, the stock may be cut the exact width of the parallel por- 
tion of the blank in the slitting shear, and then the pieces may be 
punched and cut off two at each stroke of the press, as shown in the 
die in Fig. 67. There is one inherent drawback to this form of die, 



34 



No. 6— PUNCH AND DIE WORK 



and that is the tendency of the punch to lift up the end blank while 
cutting it off and produce a badly beveled edge. But if this portion of 
the strip is securely held down by the clamping device on the die as 
shown, the punch will have the same effect on both sides of the blank, 
cutting it off squarely. The gage and stripper held down by the cap- 
screws can be made a better fit on the stock than ordinarily, because 
it is not necessary to lift it up past a stop pin fastened to the die 
to enable the operator to feed the strip. By inclining the press, 
allowing one blank to slide out when released by the clamp, and letting 
the punched one drop through, two complete blanks are produced at 
each stroke of the press, with almost no scrap. 

The extension punch and die in Fig. 67 is quite useful on work 
which is commonly beyond the scope of the press, such as the sheet 




Machinery, jV, 1'. 
Fig. 66. Die for Punching without Waste the Pieces shown in Fig. 64 

iron box shown in Fig. 63. This forms the sides of a slate-bottomed 
switch cabinet used on the old Manhattan Railway cars when they 
were equipped w-ith electricity. The operations on this box included 
the bending of the 2 by 14-inch strap iron in four places, forming the 
lap joint, and riveting same. The cut shows the punch and die 
(without necessary stops and gages) in position for bending the cor- 
ners. The front clamping plate is removed from the ram and a cast 
steel extension bolted in its place with the same bolts. The large 
hook bolt extending into the hole in the ram and drawn up by the 
nut outside, is required to support the extension during the strain of 
bending. To allow the stock to clear the front of the press when bent 
Into shape, the distance A in Fig. 67 should be a little more than 
half the width of the strap iron to be bent, and to avoid fouling the 
flywheel, corner x in Fig. 63 should be the first one bent after the lap 



SUGGESTIONS IN DIE MAKING 



35 



has been formed, and then, in rotation, corners y, z and o. When run- 
ning the press at its accustomed speed on this job the ends of the bent 
piece moved rather too fast for comfort, and it was therefore necessary 
to cut down the speed of the flywheel by inserting resistance in the 
armature circuit of the motor which drove the line shaft to which 
three of these presses were belted.* 

Method of Locating' Stock in Dies 
"When a job will not warrant the expense of a sub-die, the device 
shown in Fig. 68 will help wonderfully toward producing accurate 
punchings. To simplify the explanation, the die shown is to cut 
washers, the holes being eccentric with the outside. The die is laid out 
the same as any double die, but the stop pin G is added, and as will 
be noted, the extension K does not come out of the die. If, however. 




Fig 67. Die for Corner of Sheet Iron Box 

one depends entirely on this stop pin, the result will not be satisfac- 
tory, because, when the stock is pulled against the stop pin, the web 
between the blanked places will bend a trifle, especially if the stock is 
thin. Therefore the long pins R are added, and as these long pilots 
or traveling dowels are well pointed, and are considerably longer than 
the punches, they of course enter the holes and force the stock back 
to its proper location. The pilots fit two holes in the die, and they 
therefore act as dowels while the punch is cutting. The pilots and the 
spring butts h keep the stock pressed firmly against the gage side of 
the stripper, and the stock can vary 1/16 inch. With this construction 
the operator is enabled to keep the press running constantly to the end 
of the strip. At each stroke the punch Q cuts out the web and allows 



* H. J. Bachmann, July, 1906. 



36 



No. 6— PUNCH AND DIE WORK 



the stock to slide along to the next web, and there is absolutely no 
possibility of the stock jumping the siop. 

As washer or small wheel dies are generally made to cut four or 
more blanks at one stroke, the following method of transferring the 
holes to stripper and punch-holder will be of benefit to some mechanics. 
If the punches are small, it is advisable to make the stripper, say, 
% inch thick, and dowel it with four good-sized pins to the die. The 
holes through the stripper are bored to fit the punches nicely. This 
will act as a guide and prevents the punches from shearing. When 
the stripper is doweled to the die, we lay out the former with buttons or 
by other methods governed by the accuracy demanded, and each hole in 



J"l 



nr 



ir 



->^ 



HOLES TO FIT 
TRAVELLING DOWELS 




GAGE SIDE 
OF STRIPrEH 



Fig-. 68. Punch and Die ^^th Guide Pins 

turn is indicated and bored through the stripper and die. If the holes 
are so small that they will not readily admit boring to such length, 
the stripper may be bored and removed and the die then bored. The 
die must, of course, be fastened in such a manner that the stripper 
can be removed without loosening the die. If properly doweled, the 
punch-holder, stripper and die can be bored together, thus insuring 
perfect alignment of the punches and the die. 

Making- an Irregular-shaped Die 
Fig. 69 shows a time-saver, as the die can be made easier and better 
because the parts can be ground to size instead of the die being filed 



SUGGESTIONS IN DIE MAKING 



37 



out. Another advantage is that if the pieces warp in hardening they 
can be ground into shape again. The pieces M are shrunk on the sec- 
tions, holding tlieni securely together. The holes N are drilled for 
clearance for the emery-wheel when grinding to size. The straps M 
are made a trifle shorter than the die over all, say 1/16 inch to the foot, 
and are heated red hot in the middle and placed in position while hot, 
and rapidly chilled. After these pieces are shrunk on, the dowels are 
transferred into the bolster. 

Another good kink when making irregular-shaped punches that are 
to cut thin stock is to make them of machine steel and case-harden 
them. Soft steel, case-hardened, does not change its form as much as 











BOLSTER 












r 

M 












M 

J 




0® 


o 


® 


0, 


■0 








r 


jO 












o 

® 

o 


o 


o 

© 


o 


O 

© 






























Machi-iiery 


.NT. 



Fig. 69. Examplp of Built-up Die 

tool steel, and even if the punch does change a trifle, the interior is 
soft and can be readily forced back to position. The outside being 
hard, the punch will wear nearly as long as one made from tool steel, 
for practically the only wear on a punch is when passing through the 
stock. For thin brass the punch works well when made of tool steel 
and left soft, and when worn badly the punch can be peened on the face 
enough to upset, and then sheared into the die. "When cutting a heavy 
blank, it is a good plan to grind the die so that the surface is quite 
rough, as the high spots then cut a trifle ahead of the low points. This 
will cause the die to run longer between grindings and is also easier 
on the press, while with a die that is ground perfectly smooth the 
entire cutting surfaces of punch and die meet simultaneously and the 
entire cutting surface of punch and die are placed under a tremendous 
strain. By grinding the die slightly lower on each end, thus producing 
a shearing cut, the die will last longer. 



S8 No. 6— PUNCH AND DIE WORK 

A Kink in Hardening 
What will greatly reduce the chances of springing in hardening of 
an irregularly shaped punch or die is to thoroughly anneal it after 
it has been machined nearly to size. This will, of course, not entirely 
remove chances of accidents, as the prime cause of cracks and distor- 
tion of work is to be found in the operator's way of handling the 
piece to be hardened. An illustration of what takes place when hard- 
ening may be given by referring to the die shown in Fig. 70. If we 
place the die in the fire, the points G will heat and expand quicker 
than the main body of the die, and there must be a sort of a "pushing" 
effect between the points C and the main body of the die. For this 
reason we heat "slowly and evenly." Now, when we dip the die in the 
bath, the points C immediately become chilled, and, of course, contract 
while the main body is still red hot. Assuming that the points have 
become entirely cooled, there must be a line that separates the part 









1 1; 
C 

' — ' n 



Fig. 70. Die of Irregular Shape Subjected to Heavy Strains in Hardening 

that has been cooled off from the red-hot part. It must follow that 
when the main body begins to contract there is a powerful strain at 
the line that separates the parts contracting at different times. '' For 
this reason the die should be removed when quite warm; this allows 
the heat to run out into the points and the contraction will be more 
even. If allowed to cool in the bath there is apt to be a crack at D. 
Polish the die to draw the temper, and do not depend on getting 
an even temper by drawing the die when it is dirty, as one part may 
draw faster than another. 

Doweling Hardened Parts 
When making pieces such as sections of a built-up die, or any piece 
having dowel holes, it invariably happens that the dowel holes do not 
line up after hardening. One way to overcome this trouble is to tap 
the dowel holes a trifle larger than the dowels to be used, and after 
the piece is hardened, screw in soft plugs and file them off flush with 



SUGGESTIONS IN DIE MAKING 



89 



the work; when the piece is screwed in its proper place, the dowel 
holes are drilled and reamed through the soft screw bushings. This 
will save a great deal of unsatisfactory lapping.* 

Construction of Dies to Prevent Breakag-e in Hardening 

Another method of preventing breakage in hardening of dies with 
small projecting tongues, as shown in Fig. 70, is to construct the die 
in the manner outlined below. The die is first filed or machined in the 
regular way, with the exception that the two tongues are left out. 
In line with the center of the tongues and at a certain distance from 
the cutting edge, holes are drilled larger than the width of the tongues. 
These are taper reamed from the top with a standard taper reamer. 
A slot is then cut from the holes into the die the same size as the 









-, 



Machinery, N, F, 

Fig. 71. Method of Making Dies to Prevent Breakage in Hardening 

tongue, when the die would look as shown in Fig. 71. We now make 
two pieces to fit in the holes, and extend out the required distance, 
making sure that they will be a drive fit after hardening. It is best 
if the pieces are 1/32 inch longer than the thickness of the die, so 
that they can be ground flush after being driven into place. While 
this may increase the cost of producing the die, yet, if from any acci- 
dent one or both tongues should be broken, they are easily replaced 
without the necessity of annealing the die.** 

Fig. 72 shows a very good method of making a die that is to contain 
a number of identically shaped teeth or points, such as dies for gear 
blanks, etc. While not being the most accurate method known, it is 
considered that for all work intrusted to a punch and die the method 
illustrated will be sufficiently accurate. A set of broaches are made, 
as shown in the cut, the number of steps being governed entirely by 
the length, or depth, of the teeth. The pilot fits the hole in the die, 
which is the diameter at the top of the teeth, and each step on the 
broach is 0.002 inch larger than the preceding step. The broaches 



• F. B. Shailor, March, 1907. 
** K. L. Ross, Sepiember, 1907. 



40 



No. 6— PUNCH AND DIE WORK 



are made on centers and necked in at Q to allow clearance for the 
chips. With a cutter of the proper shape the teeth are then milled on 
the broaches, using the dividing head on the miller. After cutting 
the teeth on all of the broaches, the teeth on the punch should be cut 




^GRIND FACES AFTER HARDENING- 
Fig- 72. Broach for making Dies for Gear Blanks, etc. 

at the same setting. The broach is then hardened and ground on the 
faces as indicated. When used, each successive step is driven through 
the die until the last step is reached, and this should be driven through 
as many times as there are teeth in the broach, turning it one tooth 
each time. By doing this, whatever error may have been caused by 
hardening is overcome.* 



F. E. Shailor, January, 1904. 



CHAPTER III 



EXAMPLES OF DIES AND PUNCHES* 

In the following are given a few examples of the design and con- 
struction of dies and punches, selected because they are very interest- 
ing and ingenious in their action. The die in Fig. 73 was designed 
by Mr. Thomas Gierding, of the New Haven Clock Company. This die 
performs five distinct operations before the piece shown in the upper 
left-hand corner of Fig. 73 is dropped completed from the press. 

In constructing this die it was not deemed practicable to make it 
of one solid piece, since one small flaw would, in this case, spoil the 
entire die. A die block of machine steel was therefore used, having 
recesses counterbored for the insertion of tool steel bushings. These 
recesses w-ere accurately spaced by the method illustrated in Fig. 74. 
One side and one end of the die block were machined perfectly square, 
and a center line drawn lengthwise on the face of the block. The 
location of the recesses was approximately laid out with lead pencil 
and the recess A bored in the lathe, by strapping the block to the 
faceplate. Before loosening the straps by which the block was held, 
the parallels, B and C, bearing against the finished edges of the block, 
were strapped to the faceplate. The straps holding the block were 
then loosened and the block moved along the strip C sufficiently to 
allow for the insertion of the spacing block, D, which had previously 
been made of the required size. The die block was then fastened and 
the hole E recessed. By repeating this operation, and adding a block 
each time until all of the recesses were bored, it was possible to space 
the die far more accurately than would have been possible by the 
time-honored method of laying it out with dividers. The punch-holder 
and the stripper were then boi'ed in the same manner, using the same 
spacing blocks. 

The bushings F, G, H, I, J, K, were next made, and after being 
hardened they were lapped to size. The outside of the bushings was 
ground concentric with the hole by wringing the bushing on a piece 
of soft steel held in the chuck and turned to fit the hole in the bush- 
ing. The bushings were then forced in the die block and the die was 
completed. The punches were ground all over, to insure straightness, 
and they, in turn, were forced into the punch-holder. The drawing 
and forming punches L and M were held with setscrews to prevent 
them from being pulled out. 

In using a die containing two. or more punches, considerable trouble 
is sometimes experienced on account of the variation in width of the 
stock to be punched. Should the stripper be planed to fit one of the 
strips of stock very nicely, the chances are that the next strip would 
not enter the stripper at all. The part, N, shown in the plan of the 



• Machinery, January and August, 1904. 



42 



No. 6— PUNCH AND DIE WORK 



die, is a novel and practical way in which this trouble is overcome. 
The stripper is planed out 1/16 inch wider than the stock and recessed 
to allow the spring guide IV to slide freely when the stripper is in 




I I II L II M 

7 ^^^ f ^ J"^ 



TT" 



-^ f HjT 



tu 



r\ 



K^ 



-iCf 



v-i' I 



k'h'^ 



■ri, 



■r— P STOP PIN 



<— STRIPPER 



•':- — DIE BLOCK 




Pig. 73. Punch and Die for Performing Five Distinct Operations 

position in the die. By glancing at the sketch the reader can readily 
see how the springs keep the stock pressing against the gage side of 
the stripper. The punch does not perform any work pertaining to 



EXAMPLES OF DIES AND PUNCHES 



43 



the finished blank, but is used for cutting out the web in the stock in 
order to allow the strip to move along until the next web touches the 
stop pin. As the stop pin P does not come out of the stock it is there- 
fore impossible to "jump" the stock and make a miscut, which would 
mean disaster to the drawing and forming punches. 

After setting up the die in the press, the punches of course descend 
five times before a single finished piece appears, but thereafter a fin- 
ished piece drops at each stroke of the press. The first punch, begin- 
ning at the left, indents the stock, and the punch is so adjusted that 
the face of the punch levels the stock. The second punch pierces the 
bottom of the indentation. The next punch draws the stock, and at 
the same time, forms the feather shown in the finished piece. The 
fourth is the forming punch and the last punch does the blanking. 




j>Iachiiiery,N.T. 
Fig. 74. Spacing the Holes in the Die in Fig. 73 

Another interesting die is shown in Fig. 75. This die contains sev- 
eral novel features that will be found valuable to many engaged in 
die-making. As the sub-press die, the frames, and the power presses 
are of standard dimensions, it too frequently occurs that a die of a 
certain size requires specially made frames, and possibly a specially 
made press. The cut. Fig. 75, shows a practical way to construct a die 
that not only is a compact self-contained die, but that can be fitted to 
any style of press (of sufficient strength), having any length of stroke. 

This particular die was designed to produce the disk shown at A, 
Fig. 76, and previous to its introduction the disks were blanked out 
with a plain open die and then leveled by hand. The disks are of 
aluminum, 99 per cent pure, and, therefore, very soft, and as it is very 
essential that they should run as true as possible, great difficulty was 



44 



No. 6— PUNCH AND DIE WORK 



experienced in leveling them. The corrugating mats B B were designed 
to level the disk and also to set, or stiffen the metal, and they proved 
a success, for when the disks leave the die they are as nearly level and 
true as is possible to make, and so stiff that they can be handled quite 
roughly without injury. The disk was not corrugated its entire sur- 
face owing to the fact that the mat would be obliged to act as the 
blanking punch, and if the corrugations extended clear to the edge of 
the mat, it could not be sharpened when dull. Therefore the rings 
C D were introduced. The ring C acts as the blanking punch, and ring 
D acts as a leveling ring. The die is guided by means of two guide 
or pilot pins, E E, Fig. 76, and as the gate of the press descends, the 
rings CD are the first to act on the stock to be punched, gripping it 
from above and below and holding the stock securely. Then, as the 
press continues downward, the rings settle back, still holding the stock, 
and the mats B B grip the blank. 

The rubber spring, which is one of the features of the design, exerts 
an increasing pressure on the metal, pressing it into the corrugations 



MACH. STEEL j 
HOLDER t 



dieG 

stripper plate n 




DDWEL PIN 

SPRING rOR FORCING 



BINgDpIERCING PUNCH g 

,RING PUNCH C , Fl, 



LEVELING RING 
AND STRIPPES 
M^TS FOR CORRUGATING DISKS 



MACH. STEEL 



>"»^\j>:^:i^;^ 



Z3 



Fig. 75. Vertical Section through Sub-press Die shown in Fig. 76 

on the mats. The press is so adjusted that the ring C. which is the 
blanking punch, comes exactly flush with the die G, but does not enter. 
On the upward stroke of the press, the springs and rubber plate force 
the moving parts back to their original position, and force the disk out 
of the die, and the surplus stock off the ring C. The rubber plate can 
be advantageously used in a small place where a very strong spring 
is required. The tension or spring effect is obtained by cutting holes 
H in the plate, Fig. 77. The more holes there are in the plate, the 
weaker the tension, as the holes permit the surrounding rubber to 
squeeze into them. On the other hand if no holes were cut in the rubber 
plate, and the same fitted the recess in the die bored for it, there would 
be no more spring effect than if a metal plate were used. Rubber does 
not compress, but merely changes shape. Another novel feature is 



EXAMPLES or DIES AND PUNCHES 



45 



that the guide pins are automatically lubricated at each stroke of the 
press. The pins run in the babbitt boxes 1 1, Fig. 76, which have four 
grooves, J, cut the entire length of the babbitt and an oil chamber 
or reservoir K recessed near the top. A quantity of oil is placed in 
the bottom of the box and as the pins descend they force the oil up 
through the grooves, J, into the reservoir, and as the pins ascend they 
form a partial vacuum at the bottom of the box, which sucks the oil 
back to the bottom. 

Space will not allow describing the methods employed when making 
each part of the die, but it will suffice to say that with the exception 



TAPER DOWEL PIN 

/ 







v_ 



X T 

guide;pin_.^\ P ' 



--^ K r 



"OIL RESERVOIR 



-X- 1; 



u^ J- 



-rrt 



V. 

(I i 



^mM\ 



^^ditt- 






mti-&m 



W 







ALUMINUM DISK 0.025 INCH THICK 

Induetri.d Preaai XF. 

Fig. 76. Side Elevation of Die shown in Section in Fig. 75, and Sample of Work 

of the mats, screws and holder, the parts were hardened and accu- 
rately ground, making a smoothly running die. It might be well, 
however, to mention the method employed in making the square 
springs L. 

It is well known what a difficult job it is to wind a heavy coil spring 
and have it a given diameter on the inside and outside, when finished. 
A large spring is generally made by heating wire red hot, and winding 
as many coils as possible before cooling, then reheating and winding 
more coils. The springs L L were made by gripping a piece of round 



46 



No. 6— PUNCH AND DIE WORK 



tool steel in the lathe chuck, turning it to the given outside diameter. 
The lathe was then geared to cut a coarse pitch thread and with a 
square thread tool, the thread was cut sufficiently deep. The inside 
of the spring-to-be was then bored out to the proper diameter, leaving 
a spring the coils of which were evenly spaced, thereby causing each 
coil to perform equally its share of the work. With a wound spring 
the coils are very seldom equally spaced, and when under pressure 
there is a greater strain on the coils furthest apart, causing the spring 
to either "set" or break at that point. 




Induttrial PreM, ti.Y. 

Fig. 77. Spring Rubber Plate 



After all parts of the die were completed, the die was assembled, 
leaving out the springs. The upper and lower parts were then brought 
together until the punches entered the dies, care being exercised that 
the upper and lower parts of the die were perfectly parallel with each 
other. The boxes II were then babbitted, first treating the guide pins 
with a light coating of flake graphite and oil to prevent the babbitt 
sticking to the pins. The writer considers that a large die of the above 
description is far superior to the ordinary sub-press die, inasmuch as it 



EXAMPLES OF DIES AND PUNCHES 47 

is more compact, and also does away entirely with the cumbersome 
cast iron frame. 

Fig. 78 shows a die that is designed to take the place of the plain, 
open, double die. The ordinary double die is made with the stripper 
fastened to the die and planed out to allow the stock to slide 
through. The unsatisfactory results obtained when using a die of this 
style are well known. The greatest fault is that no two blanks are 
exactly alike, owing to the fact that the stock is wrinkled and does not 
lie level on the die. As the punches descend, they pierce the stock 
without leveling same, and as the blanks are afterward leveled, it is 
found that the pierced holes, being unevenly spaced, will not allow the 
blanks to interchange. By making the die, as shown in Fig. 78, with 
the stripper plate M fastened to the punch-holder and with a stiff coil 
spring at each corner, and so adjusted that the punches do not come 



STRAP AS USED WHEN 
SETTING UP IN PRESS 



m 






CHECK SCREW 



FOR DRIVING OUT PILOTS 



::i m I III 




P P. 



T-MZI 



I'BUANKING PUNC 



ir 



O O V-- PILOT PINS -V 



PIN TO GUIDE STOCK 




PIN TO GUIDE STOCK 



Industriat Pres»f iV,i', 
Fig. "78. Die with Stripper Attached to Punch to Flatten Stock 

quite flush with the face of the stripper, the above-mentioned trouble is 
nearly eliminated. On the downward stroke of the press the stripper M 
presses the stock firmly against the die, holding it level while the 
punches perform their work. The stock is guided by means of a small 
pin N at each end of the die. The stripper should not fit the punches; 
for if the operator should make a miscut, or should a piece of scrap 
punching get under the stripper, it would cause it to tilt and bring 
disaster to the small punches. 

Another valuable feature in this die is the manner in which the 
piercing punches are constructed. Ordinarily piercing punches are 
made solid, p,nd if one breaks, it necessitates making a whole new- 
punch or grinding the other punches down to the same length, greatly 



48 



No. 6— PUNCH AND DIE IVORK 



shortening the life of the die. The punches shown at are designed 
to overcome this trouble. A holder P is made and left soft, into which 
the punch (or rod) is inserted, being backed up by the screw Q and 
prevented from pulling out by means of the screws R. Then, should 
one of the punches "flake" off, that same punch can be ground and 
then forced out by means of the screw Q until it is at the same height 
as the others. This style of piercing punch greatly increases the life 
of a die. This die can be made either with or without the guide pins 
E E in Fig. 76. If made without the guide pins it is necessary to use 
the straps S to allow aligning the punches with the die when "setting 
up" in the press. The stripper is forced back and the straps inserted 
in the holes T T. After the die is "set up" and securely fastened, the 
straps are removed. 

All presses in which double dies are used should be provided with a 
separator, which is a piece of sheet metal fastened underneath the press 
to separate the scrap punchings from the blanks. It is frequently 

U V 

SOFT RUBBER WHEEL^ VV/\SHERS 





Jnduflnnl Pitt' 

Fig. 79. Macliine for Separating- Blanks from Stock Strips 

noticed that in factories where no separator is used, the cost of sorting 
the blanks from the scrap is in excess of the cost of blanking. A sub- 
press die leaves the blanks in a strip of stock. If the stock is over 
0.02 inch thick, considerable trouble is experienced in removing the 
blanks. Fig. 79 shows a means whereby the blanks are forced from 
the strip without marring them. JJ represents a soft rubber wheel, 
which is supported on the sides nearly to the edge by the washers Y. 
The angle iron W is provided with adjustable guides X and is recessed 
at Y to receive bushings having different sized holes. A bushing is 
inserted in the angle iron having a hole somewhat larger than the 
blanks to be forced out. The guides X are then adjusted to allow the 
strip to slide freely. The angle iron is then raised by loosening the 
bolt Z until sufBcient pressure is brought on the rubber wheel. The 
wheel being power driven, all that is necessary is to place the end of 
a strip under the rubber wheel and it will roll the strip .along, at the 
same time forcing out the blanks. 






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s 



LIBRARY OF CONGRESS 




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